Local Marine Geoid Variations and Jason-2 Bias Determination using the Gavdos Permanent Cal/Val Facility

This work outlines how changes in steep bathymetry (from 200 m to 3500 m depth over a distance of 10 km) are reflected on the determined sea surface anomalies at the Gavdos site used for satellite altimeter calibration. After almost 4 years of Jason-2 calibration activities, it has been observed that in some calibrating regions, south of Gavdos Cal/Val, and along the Passes No. 018 and No. 109, certain features in the produced bias showed a permanent characteristic that required further explanation as to its causes. Some of these features seem to be related to the general oceanographic circulation, but others are related to under-sampling of the Earth's gravity field due to the resolution of the geoid model. New reference surfaces for calibration have thus emerged. Finally, new updated values for the Jason-2 altimeter bias have been determined as 191.81 ± 2.80 mm with the geoid model and as 181.51 ± 2.73 mm when using the altimetric Mean Sea Surface model.